A substrate processing apparatus which process a substrate set in a substrate holder while keeping the process surface vertically facing down is called a face-down type vacuum processing apparatus. Since fewer foreign substances (particles) drop on the substrate surface, the face-down type vacuum processing apparatus is more advantageous than a face-up type vacuum processing apparatus which processes a substrate with its process surface vertically facing up. However, when setting the substrate in the substrate holder, the face-down type vacuum processing apparatus needs to fix the substrate to the substrate set surface of the substrate holder not to allow the substrate to drop due to gravity.
To fix the substrate, a method of clamping the substrate by holding its periphery is used. In another method, an electrode is provided in the substrate holder, and a DC voltage is applied to the electrode so that the substrate set surface electrostatically chucks (ESC) the substrate (for example, PLT1 to PLT3).
Of the above-described substrate fixing methods, the electrostatic chuck method ensures high substrate temperature controllability as compared to the clamp method. Since there are no shadows of components that hold the substrate periphery for clamping, the process can be performed more uniformly up to the substrate periphery in the vacuum process.
When the face-down type vacuum processing apparatus processes a substrate, the substrate is conventionally transported to the electrostatic chuck holder in accordance with the following steps (1) to (3).
(1) A step of placing an unprocessed substrate on the end of the transport arm of a transport robot provided in a transport chamber, transporting the substrate from the transport chamber into a substrate process chamber, and horizontally moving the substrate to a position vertically under the electrostatic chuck holder.
(2) A step, after step (1), of moving the transport arm or the electrostatic chuck holder vertically downward until the electrostatic chuck holder comes into contact with the substrate.
(3) A step of causing the electrostatic chuck holder to chuck the substrate by supplying a power for electrostatic chuck.
However, when the transport arm is extended, it cannot remain level and bends under its own weight due to the moment of inertia that acts in the gravity direction. Hence, the substrate placed on the transport arm and the electrostatic chuck holder cannot maintain the level positional relationship. When making the electrostatic chuck holder chuck the substrate, if the power is supplied to the electrostatic chuck holder that is not horizontally in contact with the substrate (point contact), the electrostatic chuck force does not act on the entire substrate surface, resulting in a chuck error. To prevent the chuck error, the substrate placing portion at the end of the transport arm uses a spring structure.
Citation List
Patent Literature
PLT1: Japanese Patent Laid-Open No. 3-54845
PLT2: Japanese Patent Laid-Open No. 5-343507
PLT3: Japanese Patent Laid-Open No. 2001-298072